Unconditionally use libc::getrandom on Illumos and Solaris

Also removes the use of `GRND_RANDOM`, which appears to be based on
outdated staements about the RNGs. For Solaris, see
[this blog post](https://blogs.oracle.com/solaris/post/solaris-new-system-calls-getentropy2-and-getrandom2).
For Illumos, the algorithms are less clear, but I don't see a clear
reason to continue using `GRND_RANDOM`.

I updated the documentation in `getrandom.rs` to full document this
decision and to have a common place listing when `getrandom(2)` became
avalible on each platform. I also updated the main lib.rs docs to point
to the correct man pages.

Note that Solaris 11.3 has a maximum buffer length of 1024 bytes,
while Illumos doesn't have this sort of issue.

Signed-off-by: Joe Richey <joerichey@google.com>

src/getrandom.rs

@@ -1,9 +1,43 @@
 //! Implementation using libc::getrandom
+//!
+//! Available since:
+//!   - Linux Kernel 3.17, Glibc 2.25, Musl 1.1.20
+//!   - Android API level 23 (Marshmallow)
+//!   - NetBSD 10.0
+//!   - FreeBSD 12.0
+//!   - Solaris 11.3
+//!   - Illumos since Dec 2018
+//!   - DragonFly 5.7
+//!   - Hurd Glibc 2.31
+//!   - shim-3ds since Feb 2022
+//!
+//! For all platforms, we use the default randomness source (the one used
+//! by /dev/urandom) rather than the /dev/random (GRND_RANDOM) source. For
+//! more information see the linked man pages in lib.rs.
+//!   - On Linux, "/dev/urandom is preferred and sufficient in all use cases".
+//!   - On NetBSD, "there is no reason to ever use" GRND_RANDOM.
+//!   - On Illumos, the default source is used for getentropy() and the like:
+//!     https://github.com/illumos/illumos-gate/blob/89cf0c2ce8a47dcf555bb1596f9034f07b9467fa/usr/src/lib/libc/port/gen/getentropy.c#L33
+//!   - On Solaris, both sources use FIPS 140-2 / NIST SP-900-90A DRBGs, see:
+//!     https://blogs.oracle.com/solaris/post/solaris-new-system-calls-getentropy2-and-getrandom2
+//!   - On Redox, only /dev/urandom is provided.
+//!   - On AIX, /dev/urandom will "provide cryptographically secure output".
+//!   - On Haiku, QNX Neutrino, DragonFly, and FreeBSD, they are identical.
 use crate::{util_libc::sys_fill_exact, Error};
 use core::mem::MaybeUninit;
 
+// On Solaris 11.3, getrandom() will fail if bufsz > 1024 (bufsz > 133120 on Solaris 11.4).
+// This issue is not present in Illumos's implementation of getrandom().
+#[cfg(target_os = "solaris")]
+const MAX_BYTES: usize = 1024;
+#[cfg(not(target_os = "solaris"))]
+const MAX_BYTES: usize = usize::MAX;
+
 pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
-    sys_fill_exact(dest, |buf| unsafe {
-        libc::getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
-    })
+    for chunk in dest.chunks_mut(MAX_BYTES) {
+        sys_fill_exact(chunk, |buf| unsafe {
+            libc::getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
+        })?;
+    }
+    Ok(())
 }

src/lib.rs

@@ -12,7 +12,8 @@
 //! | OpenBSD           | `*‑openbsd`        | [`getentropy`][7]
 //! | NetBSD            | `*‑netbsd`         | [`getrandom`][16] if available, otherwise [`kern.arandom`][8]
 //! | Dragonfly BSD     | `*‑dragonfly`      | [`getrandom`][9]
-//! | Solaris, illumos  | `*‑solaris`, `*‑illumos` | [`getrandom`][11] if available, otherwise [`/dev/random`][12]
+//! | Solaris           | `*‑solaris`        | [`getrandom`][11]
+//! | Illumos           | `*‑illumos`        | [`getrandom`][12]
 //! | Fuchsia OS        | `*‑fuchsia`        | [`cprng_draw`]
 //! | Redox             | `*‑redox`          | `/dev/urandom`
 //! | Haiku             | `*‑haiku`          | `/dev/urandom` (identical to `/dev/random`)
@@ -25,7 +26,7 @@
 //! | WASI              | `wasm32‑wasi`      | [`random_get`]
 //! | Web Browser and Node.js | `wasm*‑*‑unknown` | [`Crypto.getRandomValues`] if available, then [`crypto.randomFillSync`] if on Node.js, see [WebAssembly support]
 //! | SOLID             | `*-kmc-solid_*`    | `SOLID_RNG_SampleRandomBytes`
-//! | Nintendo 3DS      | `armv6k-nintendo-3ds` | [`getrandom`][1]
+//! | Nintendo 3DS      | `*-nintendo-3ds`   | [`getrandom`][18]
 //! | PS Vita           | `*-vita-*`         | [`getentropy`][13]
 //! | QNX Neutrino      | `*‑nto-qnx*`       | [`/dev/urandom`][14] (identical to `/dev/random`)
 //! | AIX               | `*-ibm-aix`        | [`/dev/urandom`][15]
@@ -177,12 +178,13 @@
 //! [8]: https://man.netbsd.org/sysctl.7
 //! [9]: https://leaf.dragonflybsd.org/cgi/web-man?command=getrandom
 //! [11]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
-//! [12]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
+//! [12]: https://illumos.org/man/2/getrandom
 //! [13]: https://github.com/emscripten-core/emscripten/pull/12240
 //! [14]: https://www.qnx.com/developers/docs/7.1/index.html#com.qnx.doc.neutrino.utilities/topic/r/random.html
 //! [15]: https://www.ibm.com/docs/en/aix/7.3?topic=files-random-urandom-devices
 //! [16]: https://man.netbsd.org/getrandom.2
 //! [17]: https://www.gnu.org/software/libc/manual/html_mono/libc.html#index-getrandom
+//! [18]: https://github.com/rust3ds/shim-3ds/commit/b01d2568836dea2a65d05d662f8e5f805c64389d
 //!
 //! [`BCryptGenRandom`]: https://docs.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom
 //! [`Crypto.getRandomValues`]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
@@ -249,6 +251,8 @@ cfg_if! {
         target_os = "dragonfly",
         target_os = "freebsd",
         target_os = "hurd",
+        target_os = "illumos",
+        target_os = "solaris",
         // Check for target_arch = "arm" to only include the 3DS. Does not
         // include the Nintendo Switch (which is target_arch = "aarch64").
         all(target_os = "horizon", target_arch = "arm"),
@@ -302,10 +306,6 @@ cfg_if! {
     } else if #[cfg(any(target_os = "android", target_os = "linux"))] {
         mod util_libc;
         #[path = "linux_android.rs"] mod imp;
-    } else if #[cfg(any(target_os = "illumos", target_os = "solaris"))] {
-        mod util_libc;
-        mod use_file;
-        #[path = "solaris_illumos.rs"] mod imp;
     } else if #[cfg(target_os = "netbsd")] {
         mod util_libc;
         #[path = "netbsd.rs"] mod imp;

src/use_file.rs

@@ -9,21 +9,7 @@ use core::{
     sync::atomic::{AtomicUsize, Ordering::Relaxed},
 };
 
-// We prefer using /dev/urandom and only use /dev/random if the OS
-// documentation indicates that /dev/urandom is insecure.
-// On Solaris/Illumos, see src/solaris_illumos.rs
-// On Dragonfly, Haiku, and QNX Neutrino the devices are identical.
-#[cfg(any(target_os = "solaris", target_os = "illumos"))]
-const FILE_PATH: &str = "/dev/random\0";
-#[cfg(any(
-    target_os = "aix",
-    target_os = "android",
-    target_os = "linux",
-    target_os = "redox",
-    target_os = "dragonfly",
-    target_os = "haiku",
-    target_os = "nto",
-))]
+// We always use /dev/urandom, see the comment in getrandom.rs.
 const FILE_PATH: &str = "/dev/urandom\0";
 const FD_UNINIT: usize = usize::max_value();